以二甲基苯酮建構的雙極性有機發光二極體材料

Abstract

藉由鈀金屬物催化之碳-氮鍵耦合、碳-碳鍵耦合將不同的推電子基團引入二苯基甲酮 (benzophenone) 片段的苯環中，本研究合成出四個雙極化分子 (bipolar)，化合物中有三個經單晶結構解析確認結構。由於推電子基團位於羰基的鄰位，分子的共軛性因為立體障礙而降低，使得分子擁有較高之單重激發態(HOMO與LUMO的能階差則大約為2.7−3.0 eV，HOMO能階位置則約落在5.7 eV−5.9 eV)。化合物有不錯的熱穩定性，熱裂解溫度高達300 ℃以上，玻璃轉移溫度約在 80−130 ℃。配合雙極性特徵，這些分子有利於未來作為可摻雜發光客體的主體材料。 化合物於低極性的溶劑的放光波段約為370 −550 nm之間，屬於藍光或綠光；但因立體障礙使得螢光量子產率僅達19%。化合物之螢光可能來自分子中片段的局部發光，或是電荷轉移躍遷之放光。

Different arylamines were incorporated at the ortho position of the phenyl rings of benzophenone via palladium complex catalyzed C-N or C-C coupling reaction to form bipolar compounds. Among four new compounds, three were also characterized by X-ray single crystal structural determination. Non-planar conformation of the molecules due to significant steric congestion results in weaker conjugation and larger HOMO/LUMO gap (2.7−3.0 eV). The HOMO energy level was measured to be 5.7 eV−5.9 eV. The thermal decomposition temperatures of the compounds are above 300 ℃ and the glass transition temperatures fall in the range of 80−130 ℃. The new compounds hsve potential as the host for phosphorescent emitter due to their large HOMO/LUMO gap, good thermal properties together with dipolar character. In low polar solvent, the compounds emit in the range of 370−550 nm, which is in the blue or green region. However, twisted structure of the molecules jeopardizes the emission efficiency and the best solution quantum yield only reaches 19%. The emission originates from localized π−π* transition or intramolecular charge transfer.